Previous attention has been directed to the use of vasoconstrictor agents to control hemorrhagic lesions within the gastrointestinal tract of man. Vasopressin has emerged as the pre-eminent drug of choice. Our position is that equally enthusiastic investigation is required to define the optimal vasodilator drug to apply clinically to an equally formidable array of ischemic vascular disease involving the splanchnic viscera of man and in particular his large and small bowel. We propose to compare the effects of three clinically available agents --Papaverine, Nitroprusside, and Dopamine--upon splanchnic hemodynamic event in subhuman primates. Our goal is to derive appropriate recommendations from these animal experiments to be able to suggest a drug, an appropriate concentration, route of delivery and rate of administration to best augment any specific regional splanchnic circulation in such clinical conditions where ischemia threatens not only organ, but patient survival, as well. In both "ischemic colitis" and "non-occlusive mesenteric vascular insufficiency" there exist sufficient operative mortality and morbidity to suggest as an alternative a possibly more appropriate non-operative method of management. We hope to provide the basic pharmacologic and physiologic principles of splanchnic circulatory events to enable this possibility to be a reality. We plan to address not only total organ inflow, as measured with appropriately placed electromagnetic flowmeters on arterial inflow systems, but also microcirculatory events as reflected in cardiac output distribution of radioactive microspheres and arteriovenous oxygen differences reflecting cellular energy determinants. This information should provide the clinician, whether he be a gastroenterologist, radiologist or surgeon, with the pharmacologic armamentarium to best combat clinically and certainly surgically formidably challenging problems which are appearing with increasing frequency as our patient population shows an ever drifting trend to relatively older age groups.